(457c) Modeling the Solubility of Sulfur Dioxide in Sulfuric Acid Solutions

The solubility of sulfur dioxide in sulfuric acid is an important consideration in the design of sulfur-based thermochemical cycles, particularly the Hybrid Sulfur cycle. Data culled from the literature show that for a given temperature, the solubility decreases as the sulfuric acid concentration increases from zero, reaching a minimum value. As the H2SO4 content increases past 50 mol%, the SO2 solubility begins to grow steadily, exceeding its solubility in pure water. Initial attempts to model this behavior using the ELECNRTL properties method in Aspen Plus met with limited success. Results were comparable to those obtained with OLI Systems' Mixed Solvent Electrolyte model, but different enough to cause significant disagreement in the prediction of SO2 absorber behavior using the two properties models. This presentation will document the problem and suggest an approach to fix it.